The article about the new IQ250 says that the back is very good at ISO6400. That may be the case, but it also says " In the past, with CCD digital backs it was just about impossible to use any ISO over 400 and expect decent image quality." Well, "decent image quality" is open to interpretation, but my old H3D-31 gives these results at ISO1600 when open in Phocus with default noise reduction:

Below a crop and comparison with the D800 (on top):

The complaint about poor iso performance comes from backs without micro-lenses (which can be used on technical cameras but have lower base sensitivity), but manufacturers have been selling backs with micro-lenses and a smaller sensor (the same size as the IQ250's sensor) for some time.

The phase IQ250 should improve noise level about one stop over CCD backs with micro-lenses, not much more.

An obvious practical difference between CMOS and CCD sensors is high ISO image quality. This is due to the way these sensors handle different sources of noise.

But there is another practical difference: image quality at base ISO.

Full frame transfer CCD cells and much wider, and the base ISO is lower, so the gain applied to the high quality signal also is lower. Then, you have 16 bit AD converters (not 16 "output", but 16 bits converters). This allows for wider tonal range in the shadows. And this richer tonality gamut in the shadows at base ISO is the key of the higher perceived image quality in medium format backs.

The base ISO from CMOS sensors is higher, applied to a weaker signal (smaller cells) and due to this reason usually 14 bits converters are used. The tonal gamut in the shadows is not as rich as that of CCD/16 bit systems.

If all this is correct, the high ISO comparative should be complemented with low ISO comparative (looking at tonal gamut in the shadows). This does not mean comparing at the same ISO value, but comparing at the different base ISO values (for instance, ISO 50 for the CCD and ISO 100 for the CMOS), because those systems' base ISOs are adapted to the different conditions and characteristics of each system.

So, "CMOS versus CCD" is not all the story. The idea should be "CCD/16bits/50ISO versus CMOS/14bits/100ISO" systems.

An obvious practical difference between CMOS and CCD sensors is high ISO image quality. This is due to the way these sensors handle different sources of noise.

But there is another practical difference: image quality at base ISO.

Full frame transfer CCD cells and much wider, and the base ISO is lower, so the gain applied to the high quality signal also is lower. Then, you have 16 bit AD converters (not 16 "output", but 16 bits converters). This allows for wider tonal range in the shadows. And this richer tonality gamut in the shadows at base ISO is the key of the higher perceived image quality in medium format backs.

The base ISO from CMOS sensors is higher, applied to a weaker signal (smaller cells) and due to this reason usually 14 bits converters are used. The tonal gamut in the shadows is not as rich as that of CCD/16 bit systems.

If all this is correct, the high ISO comparative should be complemented with low ISO comparative (looking at tonal gamut in the shadows). This does not mean comparing at the same ISO value, but comparing at the different base ISO values (for instance, ISO 50 for the CCD and ISO 100 for the CMOS), because those systems' base ISOs are adapted to the different conditions and characteristics of each system.

So, "CMOS versus CCD" is not all the story. The idea should be "CCD/16bits/50ISO versus CMOS/14bits/100ISO" systems.

In the end it will all come down to the weight of the system including the sensor.

The heavier the better.

If the system is heavy enough to keep the photographer at home,if he/she is not really in the mood to take images that's good. Great system!

If the system is heavy enough to force the photographer to really look at the scene, feel and explore it and deeply think about composition, viewpoint, depth of field, color and light and not to forget the message and care about each single image as much as possible that's good. Great system!

If the system is heavy enough to keep the photographer from taking a crappy scene because its not worth the hassle that's good. Great system!

In the end the advantage of one system above another should not be measured in f-stops but pounds and inches. Maybe some gifted specialist could calculate a "bulkiness factor" for each system to get a real comparison.

So what is bulkier?CCD or CMOS?

Have a nice weekendCheers~Chris

P.S. Going out now and pointing my photocopier along with a diesel aggregate at some random crap for sheer fun.

On the other hand, carrying is a Hasselblad 555 with a P45+ back with five lenses and a Sony Alpha 99 plus two "professional" zoom lenses, an Arca D4 and an RRS TVC 33S makes for some good exercise needed by elderly overweight gentlemen like me.

In the end it will all come down to the weight of the system including the sensor.

The heavier the better.

If the system is heavy enough to keep the photographer at home,if he/she is not really in the mood to take images that's good. Great system!

If the system is heavy enough to force the photographer to really look at the scene, feel and explore it and deeply think about composition, viewpoint, depth of field, color and light and not to forget the message and care about each single image as much as possible that's good. Great system!

If the system is heavy enough to keep the photographer from taking a crappy scene because its not worth the hassle that's good. Great system!

In the end the advantage of one system above another should not be measured in f-stops but pounds and inches. Maybe some gifted specialist could calculate a "bulkiness factor" for each system to get a real comparison.

So what is bulkier?CCD or CMOS?

Have a nice weekendCheers~Chris

P.S. Going out now and pointing my photocopier along with a diesel aggregate at some random crap for sheer fun.

The "about one stop better" comes from an educated comparison of CCDs and CMOS cameras having similar pixel size. For example, the Pentax 645D and the Nikon D600 have about the same pixel size and noise at the pixel level is about one stop better on the D600. The IQ250 uses pixels of 5.3 Ám, a size intermediate between the D800 and the D600. These cameras exhibit noise reduction artefacts from about iso 800 when examined at the pixel level, I don't see why the IQ250 would be any different.

I am talking about comparing pictures at 1:1 on screen here. I don't see why 5.3 Ám pixels in a Sony MF sensor would be less noisy than 5.3 Ám pixels in a different Sony sensor.

Or do you believe we should be comparing cameras of the same sensor size between generations on the final print? That is fine with me. What is the difference between the noise of the IQ250 and the IQ140 at iso 800?

That is right, mostly because CMOS sensors' active surface is smaller than CCD's active surface.

With the pixel sizes of "SLR" and "MF" sized sensors and good modern gapless micro-lenses, sensors both gather light falling over almost the entire photo site area, whether CCD or CMOS. Also, with recent designs, well capacities are about the same for either CCDs or CMOS sensors at the same pixel pitch. The differences you talk of were relevant for older CMOS designs, and perhaps still are for the far smaller photosites in compact cameras and phones, but are probably not relevant to these big, modern sensors.

With the pixel sizes of "SLR" and "MF" sized sensors and good modern gapless micro-lenses, sensors both gather light falling over almost the entire photo site area, whether CCD or CMOS. Also, with recent designs, well capacities are about the same for either CCDs or CMOS sensors at the same pixel pitch. The differences you talk of were relevant for older CMOS designs, and perhaps still are for the far smaller photosites in compact cameras and phones, but are probably not relevant to these big, modern sensors.

If the system is heavy enough to keep the photographer at home,if he/she is not really in the mood to take images that's good. Great system!

If the system is heavy enough to force the photographer to really look at the scene, feel and explore it and deeply think about composition, viewpoint, depth of field, color and light and not to forget the message and care about each single image as much as possible that's good. Great system!

If the system is heavy enough to keep the photographer from taking a crappy scene because its not worth the hassle that's good. Great system!

P.S. Going out now and pointing my photocopier along with a diesel aggregate at some random crap for sheer fun.

This is so damn right: my best photos so far come from my Mamiya RZ67 system whit no prism finder.

Said so:

I will now make a statement and question, I'm newbie on image quality, and a photographer professionally for just 5 years. But i really don't understand why everybody use the D800 as comparison meter. I own a d800 with a nice park of prime lens, i calibrate it with color passport and do my work on C1. I also own a Leaf Valeo 22.

The Valeo is 10 ( ! ) years older technology, super low to sensibility to light ( is best is iso 25, is 50 is just ok ) and incredibly slow. Also it work only with Leafcapture ( which looks designed from north korea military ).

Even so, if i shoot in my studio the image quality ( color and contrast ) is way superior to the D800. The D800 always end up with resolve complex areas in a muggy way, even when i shoot with the nikon 14-24, on a tripod, with mirror up. I mean is a great sensor, and is way more useful as portable, cheap, and usable with capture1. But if it come to Quality, real image quality, what i feel i can get from my Valeo is just superior ( and client feels the same to ).